The invention relates to a device for producing metal-free strips on vacuum-coated film webs, particularly to be used with capacitors. The devices includes a casing, a cover for sealing the casing pressure-tight, and a winding unit which has guiding and tensioning rollers rotatably supported between plates, at least one coating roller and a take-up and take-off roller as well as a coating source supported in the casing. A preferably tubular vessel is disposed transversely to the running direction of the web for holding a separating agent which can be evaporated, for example oil, by at least one nozzle so as to allow the separating agent to emerge from the vessel onto the web which passes by the outlet nozzle in direct vicinity.
A process is known for producing metal-free strips when applying a metal coating onto a strip of insulating material (German patent No. 32 24 234, to which U.S. Pat. No. 4,478,878 corresponds, and German AS No. 26 52 438) which is used for electric capacitors wherein this insulating strip is covered in the area of the metal-free strip to be produced by a continuous covering strip which sits closely on the insulating strip and moves along at the same speed. Before entering the evaporating zone, the side facing the evaporator is coated with oil and after passing through the evaporating zone. After separating covering strip and insulating strip, the coated metal is stripped off. For this purpose, the metallized insulating strip and the covering strip are first brought in contact. An oil layer is then produced by evaporation of the latter which is then deposited on the lateral surfaces of the covering strip and, to a small extent, on the adjacent surface areas of the insulating strip and, subsequently, evaporated metal is deposited.
Further, a device is known (German patent No. 12 62 732) for simultaneously applying a deposit of parallel strips of liquid or greasy substances by evaporation at a low vapor pressure, preferably oily substances, particularly onto strips used in the manufacture of electric capacitors as covering agents for a subsequent metal deposition; this device includes an evaporating vessel enclosed by a heating winding and provided with several evaporating nozzles which are fed from a supply vessel and a tubular evaporating vessel is provided which has a number of nozzles corresponding to the number and the width of the covering strips to be produced and which is provided with an inlet.
Finally, a process is known (German patent No. 11 27 474) for continuously burning away small strips from a thin metal deposit applied by evaporation, in particular, on a strip-like dielectric of an electric capacitor by means of wheel-like burn-off electrodes. Two burn-off wheels with a burning voltage source (+, -) disposed therebetween, are guided along the layer one next another and spaced apart in a small distance. The layer segments between the contact points of the wheels are burned away and the burned away material is continuously removed.